Degree of Injury and Rate of Regeneration 537 
injuries. [hus at the end of the second molting period the 
series with the least injury had regenerated 74.3 per cent of 
the cutting chela length, the second series 75.1 per cent and the 
series with the greatest injury 87.0 percent. ‘The difference be- 
tween the last and first two 1s striking especially in view of the 
difference in molting times. 
13. The Chele@ of the Crayfish, Cambarus propinquus?® 
The chelz are approximately equal in size. A comparison of 
the rate of regeneration of a chela in individuals with it alone 
removed was made with its rate in individuals in which both 
cl.elz and the last two pairs of walking legs were removed. Sev- 
enty-seven mature cray-fish ranging in cephalo-thoracic lengths 
from Io to 20 mm. were used. ‘Thirty-six of these had the lesser 
and forty-one the greater injury. The data are given in the Jour- 
nal of Experimental Zodlogy, vol. ii, no, 3, pp. 350 fil. 
It was found that the crayfish with the greater injury molted 
more rapidly than the ones with the lesser injury. “The amount 
of regeneration at the end of a molt was approximately equal in 
the two series, but because of the acceleration in the molting time 
the actual rate was greater in the series with the greater injury. 
Thus among the males in the series with the lesser injury (four- 
teen available individuals) the specific rate of regeneration” of 
the right removed chela was 0.0049 + 0.0003 against 0.0080 + 
0.0005 for the same chela in individuals with the additional eee 
(thirteen cases). 
Among females the corresponding figures are 0.0030 + 0.0001 
(fourteen cases) for the lesser injury and 0.0083 + 0.0007 (twenty 
cases) for the greater injury. 
In each case the difference is very strikingly in favor of the 
greater injury notwithstanding the considerable variations among 
individuals. 
20 Journal of Exp. Zodl., vol. ii, no. 3, p. 347- 
% The specific rate of regeneration is the rate in mms. per unit of thoracic length per day. 
